Low profile keyboard switch assembly with snap action cantilever contact

ABSTRACT

A snap-action switch is formed from a thin resilient sheet that is elastically stressed into a three-dimensional configuration. One or more bi-stable segments are provided wherein relative movement of the end of a bi-stable segment causes a snap action into a reversely-curved configuration. Switch contacts are only engaged or disengaged after the switch has snapped into a stable configuration.

United States Patent [191 Lien et a1.

LOW PROFILE KEYBOARD SWITCH ASSEMBLY WITH SNAP ACTION CANTILEVER CONTACTInventors: Wallace A. Lien, Palos Verdes Estates; Mathew Pobog, NewportBeach, both of Calif.

Becton, Dickinson Electronics Company, Ritherford, NJ.

Filed: Nov. 13, 1972 Appl. No.: 306,303

Assignee:

US. Cl. 200/5 A, 200/67 DA, 200/159 A, 200/166 BH Int. Cl. HOlh 13/44Field of Search 200/1 R, 5 R, 5 A, 6 BA, 200/17 11,18,159 B, 166 BH, 67,6 BB, 159 R, 159 A References Cited UNITED STATES PATENTS 9/1956 VerkuilZOO/159 A [4 1 Mar. 26, 1974 3,250,882 5/1966 Campbell et a1 200/159 A X3,636,284 1/1972 Wilkes 4 200/67 DA 3,600,528 8/1971 Leposavic 200/159 BX 3,290,439 12/1966 Willcox et al.. 200/5 A X 3,697,711 10/1972 Tetrick200/3 A X Primary ExaminerJames R. Scott Attorney, Agent, or Firm-MarvinH. Kleinberg [57] ABSTRACT A snap-action switch is formed from a thinresilient sheet that is elastically stressed into a threedimensionalconfiguration. One or more bi-stable segments are provided whereinrelative movement of the end of a bi-stable segment causes a snap actioninto a reversely-curved configuration. Switch contacts are only engagedor disengaged after the switch has snapped into a stable configuration.

12 Claims, 17 Drawing Figures 'MENHED UAR 2 6 i974 SHEET UF 5 LOWPROFILE KEYBOARD SWITCH ASSEMBLY WITH SNAP ACTION CANTILEVER CONTACTThis invention relates to snap-acting devices of a type in which agradual motion of one portion or a part is translated into a suddenmotion of another portion or part, and more particularly, to asnap-action switch which employs this phenomenon.

In recent years, the need has arisen for keyboards for use withsubstantially pocket-size electronic calculators. In attempting toachieve thinner and thinner profiles for the calculator, the designconstraints imposed upon the keyboard have been such that very limitedkey travel is available to establish contact for data entry purposes.From a human factors standpoint, it has been deemed desirable inkey-operated devices to-provide an audible and/or tactile signal whenthe key has been actuated.

In those applications where substantial key travel is available, themovement of the key provides the tactile signal. Yet other tactilesignals include audible clicks or mechanical detents which can be feltwhile operating the key.

In satisfying the need for a relatively thin device with only limitedkey travel available, it has been deemed desirable to provide audibleand tactile feedback which could provide a signal, within the limiteddistance of key travel available.

Prior art devices have employed snap action devices. One such deviceincludes a concave disc positioned above contacts on a printed circuitboard. When a key is depressed, the concave disc is depressed into anovercenter condition which provides a conductive link between thecontacts. Upon release of the key, the disc is restored to its normalconcave shape and the contact is broken.

Other devices employing a snap action principle have been disclosed inthe several patents to D. F. Wilkes, U. S. Pat. Nos. 3,479,624;3,543,595; 3,539,742; and 3,636,284, among others. It is noted, however,that the principles employed in the Wilkes devices add a degree ofcomplexity which is unnecessary in a simple keyboard application.

It has been deemed desirable to adapt the basic principle ofa deformedelastic member which has two positions of stability to the needs ofa keyswitch and, more particularly to a full keyboard wherein a plurality ofswitches could be fabricated as a single assembly.

According to the present invention, a single sheet of a conductivematerial is fabricated to include a cantilever arm that has twoportions. A first portion is deformed to provide a relatively shortersupport arm. A remaining, relatively longer, tongue member is, as aresult stressed into a convex or concave configuration to allow for thedifference in length. At the free end of the cantilever there isprovided a contact which is adapted to engage a terminal. In a preferredembodiment, the contact is bifurcated.

As a force is applied near the free end of the cantilever, thecantilever, as a unit, is bent. A fulcrum or support is provided underthe relatively longer, tongue portion which bends until the forcesholding it in one of its stable curved configurations are overcome,causing it to snap to its opposite curvature. An additional force andmotion is imparted to the free end of the cantilever member in thedirection of motion, closing the contact.

The material, in a preferred embodiment, is a spring material, such asphosphor bronze, beryllium copper or stainless steel, that provides anaudible click as the tongue portion snaps into its second stableconfiguration. This imparts to the operator both an audible and atactile signal that the switch has been operated and that the contacthas been made. As the key is released, changes on the forces on thetongue portion cause it to snap to its opposite or initial curvature.The snap upon opening again provides an audible and tactile signal tothe operator that the contact has been opened.

'The switch is carefully designed so that contact can not be made andreleased by teasing" the switch with slight increases or decreases ofpressure on the key mechanism. Further, the snap action provides a moreor less standardized force of contact closure, substantially independentof the mode of operating the key. Once the switch is closed, after thesnap action has taken place, additional pressure on the key will notincrease the pressure between the movable and stationary contacts of theswitch since it is desirable to have contact force independent ofoperator force.

In alternate configurations, a plurality of snap action switch membersmay be fabricated from a single sheet of material to faciliate assemblyinto a keyboard. The movable contacts can be designed to cooperate withvarious types of stationary contacts. In different applications, one mayemploy a flat contact pad on a printed circuit board, a post or terminalon a base plate or board, or an elevated contact area on a printedcircuit board.

By appropriate shaping of the movable contacts, each type of stationarycontact can be accommodated. Further, the sheet can be designed so thatgroups of switches can be electrically isolated. from other switches orgroups of switches. Contacts can easily be supplied to establish aseparate electrical circuit to each key or group of keys.

The novel features which are believed to be characteristic of theinvention, both as to organization and method of operation, togetherwith further objects and advantages thereof will be better understoodfrom the following description considered in connection with theaccompanying drawings in which several preferred embodiments of theinvention are illustrated by way of example. It is to be expresslyunderstood, however, that the drawings are for the purpose ofillustration and description only and are not intended as a definitionof the limits of the invention.

FIG. 1 is a perspective of a keyboard employing the present invention;

FIG. 2 is a side sectional view of the keyboard of FIG. 1, FIGS. 2A-2D,inclusive, illustrating keys in actuated and unactuated conditions;

FIG. 3 including FIGS. 3A and 3B is a front section view of an actuatedand unactuated key 12C of FIG. 2, taken along line 3-3 of FIG. 2C takenin the direction of the appended arrows;

FIGS. 4A and 4B are a perspective view of a switch in the open andclosed positions, respectively;

FIG. 5 is a top view of a plurality of switch members according to oneemployment of the invention at an early state of fabrication;

FIG. 6 is an enlarged view of one of the switches of FIG. 5;

FIG. 7 is a side view of the switch of FIG. 6 at a later stage infabrication; and

FIG. 8, including FIGS. 8A, 8B, and 8C, is an end view of a key switchcombination, illustrating an alternative contact configuration.

Turning first to FIG. 1, there is shown in perspective view, a lowprofile keyboard 10 according to the present invention. Included are aplurality of individual keys 12 which are arranged in groups such as anumerical group 14 and different function groups 16, 18. In theillustrated embodiment, a printed circuit extends from the end of thekeyboard 10 and is adapted to be coupled to an appropriate connector orwires (not shown) which electrically interconnect the keyboard 10 to asystem.

According to the present invention, each key 12 has a limited verticaltravel available to it, and, accordingly, must provide adequate tactileand auditory clues to the user when a key 12 is either actuated orreleased.

Turning next to FIG. 2, there is shown in side section a plurality ofdiffering keys 12A-12D, inclusive. Each of these keys is separatelyillustrated in the enlarged sectional views of FIGS. '2A-2D, inclusive,respectively. It will be noted that each of the keys 12A through 12Ddiffers slightly in design detail and have been included as illustrativeof alternative approaches that can be taken to the design of aparticular key.

In FIG. 2, there can be clearly seen the several ele ments that combineto form the keyboard. A frame member 22 overlies an insulating sealermembrane 24 and a switch plate 26, includes all of the movable switchcontacts. A spacer plate 28 supports the switch plate 26 and a printedcircuit board 30, which contains the stationary contacts, acts as abottom or base plate.

In FIG. 2A, a first key switch 12A is shown having projecting lugs atthe front and rear of the key. A rear lug 32 rides in an appropriateslot 34 and the key 12A is mounted to pivot about that point ofattachment. A forward lug 36 is provided to limit upward key travel andcooperates with an overhanging lip 38 in the key plate 22.

A switch cam 40 engages a movable switch member 42, which is an integralpart of the switch plate 26. The movable switch member 42 is actuatedthrough the insulating sealer membrane 24. As the key 12A is depressed,the cam 40 exerts a downward force on the movable switch portion 42until a stationary switch contact 44 is engaged.

In the illustrated embodiment, the stationary contact 44 is an elevatedportion of the base plate printed circuit board with suitable contactmaterial 46 integral therewith to complete a circuit with the movableswitch portion 42.

FIGS. 2B through 2D, inclusive, illustrate alternative switchconfigurations in both actuated and unactuated positions. FIG. 2B, showsa key 12B which lacks a front lug but provides, to service the samefunction, side lugs 368 which limit the upward travel of the key 12b.All other elements of the key assemblies of FIGS. 28 through 2D aresubstantially the same as in FIG 2A. The same reference numerals withthe suffix 8" appended thereto have been applied to the components ofFIG 2B. The remaining FIGS. 2C and 2D have not been described in detail.

A front view of the key 12C, for example, is shown in FIG. 3 whichincludes FIG. 3A corresponding to the key 12C in the unactuatedconfiguration, and FIG. 3B which is a view of the key 12C when actuated.As is shown, a movable contact 42C is disengaged from stationary contact44C in FIG. 3A, but is shown in contact in FIG. 3B, as the key 12C isshown in the depressed or actuated configuration.

In FIG. 4, including FIGS. 4A and 4B, a single switch 48 according tothe present invention is shown in perspective view. FIG. 4A shows theswitch 48 in the open configuration while FIG 4B shows the switch 48 inthe closed configuration. The key, frame member and sealer membrane ofFIG. 2 have been omitted for clarity of explanation of the operation ofthe switch 48.

A switch plate 50 is made of a conductive material which is alsoresilient such as phosphor bronze, beryllium copper, or stainless steel.Th movable switch portion 52 is cut or otherwise fabricated from themain plate 50. The switch plate 50 rests on a spacer plate 54 which, inturn, rests on a printed circuit board 56. In this embodiment, theprinted circuit board 56 has a conductive pad 58 as the stationaryswitch contact.

The movable switch member 52 includes a bifurcated contact pair 60 atthe free end of the movable switch member 52. In this embodiment, thecontact pair 60 is bent toward the base plate to assure good electricalcontact with the pad 58.

A pair of slots 62 running from the fixed end toward the movable end ofthe movable switch member 52 divides it into a central tongue portion 64and supporting arm portions 66. A crimp or bend 68 is placed in thesupporting arm portion 66 near the point of attachment to the switchplate 50.

The crimp 68 has two purposes. First, it imparts a generally upward biasto the switch member 52 and, second, it shortens the supporting arms 66relative to the tongue portion 64, thereby introducing a curvature intothe tongue portion 64 extending out of the plane of the movable switchmember 52. The spacer plate 54 provides a support tab 70 whichinfluences or controls the operation of the tongue, as to where itsnaps, and how crisply it does so.

As the movable switch member 52 is cammed downward by the action of thekey, the arm portions 66 pivot about the point of attachment behind thecrimp 68.

The tongue portion 64, however, is constrained to pivot about thestiffening tab 70 acting as a fulcrum. Accordingly, the movable arm 52moves downward. The free end continues to bend until the tongue portion64 is substantially straight. As the free end continues to movedownward, the tongue portion 64 snaps into a reverse curvature, reducingthe force applied to the key top by the finger.

The dimensions and placement of the movable switch members 52 are suchthat the continued downward movement of the free end does not engagecontact 60 with pad 58 until after the tongue portion 64 has reversedits curvature. The contact pair 60 can be bent or shaped to adjust thepoint of switch travel at which the contact is made."

While FIGS. 4A and 48 have shown a flat pad, stationary contact 58 incooperation with a bent contact pair 60, other alternative embodimentsutilizing a raised stationary contact such as is shown in FIGS. 2 and 3would operate in substantially the same fashion,

with the movable switch arm contacts being coplanar with the body of thearm.

Turning next to FIG. 5, there is shown a switch plate 126, fabricatedfrom a single sheet of material. As shown, sheet 126 can be punched,stamped or chemically etched or milled into the configuration shownwherein a plurality of movable switch members 152 are provided. Aplurality of contact tabs 130 are provided to engage conductors on aprinted circuit base plate (not shown) to complete the electricalcircuit of individual switches.

As shown, the switch members are adapted to be isolated from each otherin groups corresponding to the groups shown in FIG. 1, such as anumerical group 114, and the function groups 116 and 118. This would beaccomplished by severing the connections at the parting lines so thateach switch within a group would be electrically interconnected but thatswitch groups would be isolated from each other. As shown, a separatecontacting tab 130 is provided for each of the potential groups. I

Turning to FIG. 6, there is shown in somewhat greater detail, one of themovable switch segments of the plate 126 of FIG. 5. As shown, andcorresponding to the reference numerals of FIG. 4, the movable switchmember is initially formed from a planar blank and has the contact 160at the free end of a cantilever arm. A pair of slots 162 divide thecantilever into central tongue portion 164 and supporting arms 166.

In FIG. 7, which is an enlarged side view of the switch of FIG 6, acrimp or bend 168 is made in the arm portions 166 which imparts a biasto the arm 152. As shown, the supporting arms I66 are in the plane ofthe movable member while the tongue portion 164 has a curvature imposedupon it out of that plane.

Turning finally to FIGS. 8A, 8B and 8C, there are shown alternativestationary contact configurations suitable for use in cooperation withthe movable switch of the present invention. FIG. 8A shows a nail heador rivet contact 180 which can be electrically connected to circuitsfrom the bottom side of the base plate member 182. FIG. 88 illustrates acontact 184 which is raised and formed from the base plate material, andwhich is covered with a conductive material 186, as shown in FIGS. 2 and3. FIG. 8C illustrates a flat pad contact 188 as shown in FIG. 4.

Thus there has been shown a novel switch configuration which provides atactile and audible signal when actuated. A movable cantilever memberincludes a prestressed portion that has a first curvature with thecantilever in a first position. As the cantilever moves to a secondposition through a center position, the prestressed portion reverses itscurvature with an audible snap or click and which accelerates theactuation of the switch. Releasing the switch, the cantilever moves tothe first position and the prestressed portion again reverses itscurvature to its first curvature.

A plurality of similar switches are easily fabricated from a sheet ofspring material using mass production tecnhiques. A keyboard can bequickly fabricated using such a switch plate together with a printedcircuit board containing stationary contacts, and a spacer plate withkeys and a frame member added. The combination is easily assembled.

We claim:

1. A snap action switch swinger adapted to cooperate with a stationaryswitch contact comprising:

a cantilever arm member extending from a conductive spring body memberand said arm member having a fixed end and a free end;

separating means for dividing said cantilever arm member into a supportportion and a tongue portion, intermediate said fixed and free ends;

means for introducing a difference in length as between said tongueportion and said support portion, said means imparting a curvature tothe relatively longer portion, biasing said cantilever arm member into afirst, stable, non-actuated configuration; and

contact means at said free end, said cantilever arm member beingoperable, in response to movement in a direction opposite to thecurvature of said longer portion, to reverse the curvature of saidlonger portion, biasing said cantilever arm member into a second, stableactuated configuration with said contact means in operational proximityto the stationary contact.

2. The snap action switch swinger of claim 1, above, wherein saidseparating means include a pair of slots extending from said fixed endtoward said free end, the elongated portion intermediate said slotsbeing considered said tongue portion and said means for introducing adifference in length include a crimp in said support portion therebyshortening said support portion relative to said tongue portion.

3. The snap action switch swinger of claim 1, above, wherein saidcontact means include a pair of opposed cantilever arm members,extending in a direction substantially orthogonal to said cantilever armmember direction of extension.

4. A snap action switch assembly including in combination:

cantilever arm means extending from a conductive spring body member,said cantilever arm means having a fixed end and a free end;

separating means for dividing said cantilever arm means into anelongated support portion and an elongated tongue portion, intermediatesaid fixed and free ends;

means for introducing a difference in length as between said tongueportion and said support portion for imparting a curvature to therelatively longer portion and for biasing said cantilever arm means intoa first, stable, non-actuated configuration in a first direction;

contact means at said free end of said cantilever arm means; and

spacer support means below said conductive spring body member andincluding a tab portion extending under said longer portion to provide abending point for said longer portion different from the bending pointof said shorter portion in response to motion applied to said cantileverarm means;

whereby motion of said cantilever arm means in a second direction,opposite to said first direction, causes said longer portion to engagesaid tab portion, forcing said longer portion to reverse its curvatureinto a second table actuated configuration for said arm means, reducingthe magnitude of the force required to continue motion of saidcantilever arm means in said second direction.

5. The snap action switch assembly of claim 4, above,

including base plate means adjacent said spacer support means, said baseplate means including fixed contact means operatively positioned toengage said contact means when said cantilever arm means are in thesecond stable actuated configuration.

6. The snap action switch assembly of claim 4, above, further includingpush button means adjacent said cantilever arm means for impartingmotion in said second direction to said cantilever arm means, foractuating the switch assmebly and for maintaining the switch assembly inthe second stable actuated configuration against the bias in said firstdirection, in response to continued operation of said push button means.

7. The snap action switch assembly of claim 4, above, wherein saidrelatively longer portion is said tongue portion and said relativelyshorter portion is said support portion.

8. A snap action switch assembly including in combination:

a. a conductive switch plate having a plurality of cantilever armsextending therefrom, each having a fixed end and a free end;

b. means for providing each of said cantilever arms with a tongueportion and a support portion, and for introducing a difference inlength as between said tongue portion and said support portion to imparta curvature to said tongue portion in a primary stable configuration;

c. spacer support means adjacent said conductive switch plate includinga plurality of tab portions, each underlying the tongue portion ofa oneof said arms, each said tab portion supplying a fulcrum to itsassociated tongue portion different from the corresponding supportportion; and

d. base plate means, adjacent said spacer support means, having aplurality of stationary contact elements each adapted to be engaged by acorresponding one of said cantilever arm free ends, whereby movement ofaone of said cantilever arms in the direction of said base plate causessaid tongue portion to engage said tab portion, reversing the curvatureof said tongue portion into a secondary, stable configuration with saidcantilever free end engaging said stationary contact elementcorresponding thereto, and whereby in the absence of a force holdingsaid arm in said secondary, stable configuration, said arm returns tosaid primary stable configuration.

9. The snap action switch assembly of claim 8, above, further including:

a plurality of keys, each adjacent a one of said cantilever arms forimparting motion to said arms, thereby placing said arms in thesecondary stable configuration with said stationary contact engaged withthe corresponding arm free end. 10. A keyboard assembly comprising, incombination:

a. actuator means comprising a plurality of individually operable keymembers adapted to be depressed; b. a plurality of cantilevered, movablecontact members having free ends and fixed ends, mounted adjacent saidactuator means, each in operable proximity to a corresponding one ofsaid plurality of key members, each of said movable contact membershaving an upward bias and a first, relatively stable configuration in anonactuated, up position, and a second, relatively stable configurationin an actuated, down position; c. support means comprising a framecontaining said plurality of movable contact members, and a plurality offulcrum elements, each positioned adjacent and below the fixed end of acorresponding movable contact member; and d. a plurality of fixedcontacts spaced apart from said plurality of movable contacts, eachadapted to be engaged by a corresponding one of said plurality ofmovable contact members free ends, each of said movable contact membersbeing operable in response to a limited depression of a correspondingkey member to partially pivot against said fulcrum element against saidupward bias to change from said first to said second relatively stableconfiguration, for electrically engaging said fixed and movablecontacts,

whereby engagement of said contacts is independent of further depressionof said key member.

11. The keyboard assembly of claim 10, above, wherein each of saidcantilevered movable contact members comprise separating means fordividing said contact member imto a support portion and a tongue portionintermediate said free ends including a pair of separate slots extendingbetween said fixed and free ends; and means for introducing a differencein length as between said tongue portion and said support portion,imparting a curvature to the relatively longer portion, which in saidfirst relatively stable configuration is a downward curvature and insaid second relatively stable configuration is an upward curvature.

12. The keyboard assembly of claim 11, above, wherein said means forintroducing a difference in length comprises a crimp in said supportportion adjacent said contact member fixed end, whereby said tongueportion is the relatively longer portion, said crimp also providing saidupward bias.

1. A snap action switch swinger adapted to cooperate with a stationaryswitch contact comprising: a cantilever arm member extending from aconductive spring body member and said arm member having a fixed end anda free end; separating means for dividing said cantilever arm memberinto a support portion and a tongue portion, intermediate said fixed andfree ends; means for introducing a difference in length as between saidtongue portion and said support portion, said means imparting acurvature to the relatively longer portion, biasing said cantilever armmember into a first, stable, non-actuated configuration; and contactmeans at said free end, said cantilever arm member being operable, inresponse to movement in a direction opposite to the curvature of saidlonger portion, to reverse the curvature of said longer portion, biasingsaid cantilever arm member into a second, stable actuated configurationwith said contact means in operational proximity to the stationarycontact.
 2. The snap action switch swinger of claim 1, above, whereinsaid separating means include a pair of slots extending from said fixedend toward said free end, the elongated portion intermediate said slotsbeing considered said tongue portion and said means for introducing adifference in length include a crimp in said support portion therebyshortening said support portion relative to said tongue portion.
 3. Thesnap action switch swinger of claim 1, above, wherein said contact meansinclude a pair of opposed cantilever arm members, extending in adirection substantially orthogonal to said cantilever arm memberdirection of extension.
 4. A snap action switch assembly including incombination: cantilever arm means extending from a conductive springbody member, said cantilever arm means having a fixed end and a freeend; separating means for dividing said cantilever arm means into anelongated support portion and an elongated tongue portion, intermediatesaid fixed and free ends; means for introducing a difference in lengthas between said tongue portion and said support portion for imparting acurvature to the relatively longer portion and for biasing saidcantilever arm means into a first, stable, non-actuated Configuration ina first direction; contact means at said free end of said cantilever armmeans; and spacer support means below said conductive spring body memberand including a tab portion extending under said longer portion toprovide a bending point for said longer portion different from thebending point of said shorter portion in response to motion applied tosaid cantilever arm means; whereby motion of said cantilever arm meansin a second direction, opposite to said first direction, causes saidlonger portion to engage said tab portion, forcing said longer portionto reverse its curvature into a second table actuated configuration forsaid arm means, reducing the magnitude of the force required to continuemotion of said cantilever arm means in said second direction.
 5. Thesnap action switch assembly of claim 4, above, including base platemeans adjacent said spacer support means, said base plate meansincluding fixed contact means operatively positioned to engage saidcontact means when said cantilever arm means are in the second stableactuated configuration.
 6. The snap action switch assembly of claim 4,above, further including push button means adjacent said cantilever armmeans for imparting motion in said second direction to said cantileverarm means, for actuating the switch assmebly and for maintaining theswitch assembly in the second stable actuated configuration against thebias in said first direction, in response to continued operation of saidpush button means.
 7. The snap action switch assembly of claim 4, above,wherein said relatively longer portion is said tongue portion and saidrelatively shorter portion is said support portion.
 8. A snap actionswitch assembly including in combination: a. a conductive switch platehaving a plurality of cantilever arms extending therefrom, each having afixed end and a free end; b. means for providing each of said cantileverarms with a tongue portion and a support portion, and for introducing adifference in length as between said tongue portion and said supportportion to impart a curvature to said tongue portion in a primary stableconfiguration; c. spacer support means adjacent said conductive switchplate including a plurality of tab portions, each underlying the tongueportion of a one of said arms, each said tab portion supplying a fulcrumto its associated tongue portion different from the correspondingsupport portion; and d. base plate means, adjacent said spacer supportmeans, having a plurality of stationary contact elements each adapted tobe engaged by a corresponding one of said cantilever arm free ends,whereby movement of a one of said cantilever arms in the direction ofsaid base plate causes said tongue portion to engage said tab portion,reversing the curvature of said tongue portion into a secondary, stableconfiguration with said cantilever free end engaging said stationarycontact element corresponding thereto, and whereby in the absence of aforce holding said arm in said secondary, stable configuration, said armreturns to said primary stable configuration.
 9. The snap action switchassembly of claim 8, above, further including: a plurality of keys, eachadjacent a one of said cantilever arms for imparting motion to saidarms, thereby placing said arms in the secondary stable configurationwith said stationary contact engaged with the corresponding arm freeend.
 10. A keyboard assembly comprising, in combination: a. actuatormeans comprising a plurality of individually operable key membersadapted to be depressed; b. a plurality of cantilevered, movable contactmembers having free ends and fixed ends, mounted adjacent said actuatormeans, each in operable proximity to a corresponding one of saidplurality of key members, each of said movable contact members having anupward bias and a first, relatively stable configuration in anonactuated, ''''up'''' position, and a second, relatively stableconfiguration in an aCtuated, ''''down'''' position; c. support meanscomprising a frame containing said plurality of movable contact members,and a plurality of fulcrum elements, each positioned adjacent and belowthe fixed end of a corresponding movable contact member; and d. aplurality of fixed contacts spaced apart from said plurality of movablecontacts, each adapted to be engaged by a corresponding one of saidplurality of movable contact members free ends, each of said movablecontact members being operable in response to a limited depression of acorresponding key member to partially pivot against said fulcrum elementagainst said upward bias to change from said first to said secondrelatively stable configuration, for electrically engaging said fixedand movable contacts, whereby engagement of said contacts is independentof further depression of said key member.
 11. The keyboard assembly ofclaim 10, above, wherein each of said cantilevered movable contactmembers comprise separating means for dividing said contact member imtoa support portion and a tongue portion intermediate said free endsincluding a pair of separate slots extending between said fixed and freeends; and means for introducing a difference in length as between saidtongue portion and said support portion, imparting a curvature to therelatively longer portion, which in said first relatively stableconfiguration is a downward curvature and in said second relativelystable configuration is an upward curvature.
 12. The keyboard assemblyof claim 11, above, wherein said means for introducing a difference inlength comprises a crimp in said support portion adjacent said contactmember fixed end, whereby said tongue portion is the relatively longerportion, said crimp also providing said upward bias.